A multi-shaft kneading machine is known that performs various kinds of processing that is aimed at homogenizing, modifying the properties of and adding materials to synthetic resin material. A biaxial kneading machine described in Patent Literature 1, which is an example of the multi-shaft kneading machine, has a cylinder having an inner space and two screws that extend in parallel with each other in the cylinder. The processing mentioned above is performed by the two screws rotating in the same direction or in opposite directions. Synthetic resin material is supplied from a supply port of the multi-shaft kneading machine, is conveyed by a conveying part, is kneaded by a kneading part, and is then discharged from an ejection port.
A gate part that adjusts the degree of kneading is provided on the outlet side of the kneading part. The gate part adjusts the degree of kneading of the synthetic resin material in the kneading part by variably controlling the sectional area of a channel through which the synthetic resin material passes. JP2000-309018A describes a gate part having gate rods. A pair of gate rods that are opposite to each other and that sandwich two screws is provided. The gate rod can be rotated around an axis of rotation that is orthogonal to a direction in which the screws extend. The gate rod includes two recess parts. Corresponding recess parts of the pair of gate rods are opposite to each other in order to form spaces through which the two screws penetrate. The sectional area of the channel around the screw is changed by the rotation of the gate rods. As a result, the degree of kneading of the synthetic resin material can be adjusted. The gate rod has a generally cylindrical outer shape.
The gate rods can be rotated between a minimum degree-of-opening position where the area of the channel that is formed by the screw and the gate rods is minimized and a maximum degree-of-opening position where the area of the channel is maximized. The recess part of the gate rod has a channel forming surface that forms a part of the channel and a first contact surface that is cut out from the channel forming surface. When the gate rods are rotated to the minimum degree-of-opening position, the first contact surfaces come into surface contact with the outer surface of the screw in order to limit the channel. The channel forming surface has the same radius of curvature as the cylinder, and the first contact surface has the same radius of curvature as the screw.
Patent Literature 1: JP2000-309018A